ABSTRACT
Objective To investigate the value of serum IgG4 level in the differential diagnosis of IgG4-related pancreatic and hepatobiliary disease (IgG4-PHD) and non-IgG4-related disease (non-IgG4-RD). Methods Clinical data were collected from 491 patients who were hospitalized and 50 individuals who underwent physical examination in Huaian No. 1 People's Hospital Affiliated to Nanjing Medical University, Subei People's Hospital, and The First Affiliated Hospital of Xuzhou Medical University from August 2014 to April 2021. The 491 patients were divided into IgG4-PHD group with 20 patients, non-IgG4-RD autoimmune disease group with 431 patients (104 patients with systemic lupus erythematosus, 79 with rheumatoid arthritis, 174 with Sjogren's syndrome, 16 with ankylosing spondylitis, 11 with scleroderma, 4 with adult-onset Still's disease, 30 with myositis, 3 with psoriasis, and 10 with primary sclerosing cholangitis), and malignant pancreatic/hepatobiliary tumor group with 40 patients, and the 50 individuals undergoing physical examination were enrolled as healthy control group. Scattering immunoturbidimetric assay was used to measure serum IgG4 concentration. The two-sample Mann-Whitney U test was used for comparison of normally distributed continuous data between groups, and the Fisher's exact test was used for comparison of categorical data between groups. The receiver operating characteristic (ROC) curve was plotted to determine the optimal cut-off value of serum IgG4 in the diagnosis of IgG4-PHD. Results The IgG4-PHD group had a significantly higher serum IgG4 level than the non-IgG4-RD autoimmune disease groups, the malignant pancreatic/hepatobiliary tumor group, and the healthy control group (all P < 0.05), and the Sjogren's syndrome group had a significantly lower serum IgG4 level than the healthy control group ( Z =2.958, P < 0.05). With serum IgG4 ≥1.35 g/L and IgG4 ≥2.01 g/L as the cut-off values, the IgG4-PHD group had a significantly higher positive rate than the non-IgG4-RD autoimmune disease group and the healthy control group (all P < 0.05). The ROC curve analysis showed that IgG4 had an area under the ROC curve of 0.980 in the differential diagnosis of IgG4-PHD and non-IgG4-RD autoimmune diseases, with a sensitivity of 100.00% and a specificity of 94.00% at the optimal cut-off value of 2.21 g/L. Conclusion Serum IgG4 level may also increase in non-IgG4-RD autoimmune diseases, while the cut-off value of 2.21 g/L can improve the differential diagnosis of IgG4-PHD and non-IgG4-RD autoimmune diseases, which requires further verification in clinical practice.